The present invention provides an improvement to the read/write head actuator assembly in small disc drive systems. The preferred embodiment is designed to connect a printed circuit cable (PCC) to the actuator arm such that the bias due to the cable upon the arm is minimized and the residual bias is consistent during repeated arm rotation. Consistency in the bias is required so that the actuator control motor may provide the proper force to overcome the bias and position the actuator arm relative to the disc in a repeatable fashion.
In a disc drive, the read/write heads are attached to an actuator arm. A voice coil magnetic motor provides the force to move the arm about a pivot and position the heads over a desired portion of the disc. This arrangement is known as a head disc assembly.
The information supplied to the heads (write) or supplied by the heads (read) is normally carried by small wires from the heads to a point near the actuator arm pivot. A flexible printed circuit cable (PCC) is secured to the arm and the small signal carrying wires are soldered to the PCC. Additionally, the PCC carries signals to activate the moving coil motor and effectuate actuator arm rotation. In many disc drives, the PCC carries the read head signals from the moving arm to a fixed circuit board having a preamplifier to amplify the signals before sending them to a signal processing circuit elsewhere in the disc drive.
In many previous disc drive designs, the flexible PCC was bent to form an arc between the circuit board and the arm. The end attached to the arm is usually secured via an adhesive. The use of adhesive within the disc housing is usually to be avoided, except in arrangements where no other choice is apparent, because adhesives may outgas and produce particles which will contaminate the discs and or the heads. Additionally, the use of adhesives in manufacturing makes repeatable assembly very difficult. Adhesives are used in this situation to avoid adding mass to the actuator arm. Disc drive designers have deemed a small amount of adhesive as necessary at the expense of outgassing problems and manufacturing repeatability.
Another area of concern is the arc in the PCC applying a force upon the arm and pivoting the arm to an arbitrary position. This force is called bias. The bias must be overcome by the actuator motor to reposition the arm. Thus, a large bias requires a powerful motor to overcome the bias.
In small disc drives, it is desired to design the actuator motor as small as possible. This requires using low mass parts, reducing bearing friction, and minimizing the bias. In addition to minimizing the bias, the bias must be consistent during repeated operation of the actuator arm. A consistent bias means the actuator motor can be designed and operated to overcome a specific, known bias over the full operating range of the actuator arm.
Past attempts at minimizing the bias have resulted in complex cabling strategies. One such connection disclosed in U.S. Pat. No. 4, 933, 785 maintains two opposing bend radii in the PCC to obtain counteracting bias forces resulting in bias minimization. A simplified cabling assembly is desired to reduce production costs.
An objective of the current invention is to provide an attachment apparatus which maintains a small bias that is consistent during repeated arm rotations. In particular, the apparatus maintains a specific bend radius in the PCC to effectuate the bias consistency, but uses a simple arrangement.
Another object of the present invention is to provide a PCC attachment means which does not use adhesive. In particular the invention secures the PCC using a bracket, clip, and screw arrangement.